The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
In an internal combustion engine (ICE) fuel may be injected into an intake manifold, for example single port injection per fuel bank, per engine or multi-ports injection per cylinder. Alternatively or additionally, fuel may be injected directly into cylinders. The fuel is then mixed with air to form an air/fuel mixture. The air/fuel mixture is combusted to generate torque. The fuel and air may be controlled such that the engine maintains an air-to-fuel ratio at stoichiometry. The engine may operate using fuels with different stoichiometric values, such as a gasoline and ethanol blend. As the percentage of each fuel in the overall fuel mixture changes, the stoichiometric value may change.
The stoichiometric value of a fuel mixture may be measured to allow for optimal operation of the engine based on the particular fuel mixture. The engine system may change the relative amounts of air and fuel delivered to the cylinders based on the stoichiometric value for the fuel mixture.
The volatility or the measure of how quickly fuel vaporizes changes with the type of fuel and the operating engine temperature. For example, during cold starts when an engine is at an ambient temperature or is not up to a normal operating temperature, fuel vaporizes at a reduced rate. This affects the ability of an engine to maintain a predetermined idle speed.